1. Field of the Invention
The present invention relates to glycol starting materials containing dispersed superfine ceramic powder aggregates that enables polyester molded bodies to be thin and to have a fine fiber size, as well as to improve the transparency thereof, when the material is used for manufacturing polyester molded bodies suitable for films and threads.
2. Description of the Related Art
Conventional polyesters have been manufactured by a process comprising: esterifying a polycarboxylic acid such as terephthalic acid with an alkylene glycol such as ethylene glycol at 260° C. in a reaction vessel; forming a polyester polymer by allowing the polymerization reaction to proceed; and quenching the polyester polymer by ejecting the reaction product onto the surface of a quenching rotary drum for forming a film, or allowing the polyester polymer to spin out of fine perforation holes on a die having a number of perforation holes on its surface and rotating at a high speed like a top for spinning fibers.
It is known in the art that the type of glycol starting material used for manufacturing the polyester molded body contains 1 to 20% by weight of a superfine ceramic powder comprising silicon oxide (denoted as SiO2 hereinafter), aluminum oxide (denoted as Al2O3 hereinafter) and titanium oxide (denoted as TiO2 hereinafter) relative to the content of the glycol, in order to improve abrasion resistance and compatibility with dyes, and for preventing blocking.
The superfine ceramic powder to be used for dispersing into the glycol starting material is usually manufactured by a gas-phase reaction of SiCl4, AlCl3 or TiCl4 with hydrogen and oxygen in a combustion burner flame. The superfine ceramic powder obtained has a very fine mean particle size of 40 nm or less, as determined by averaging the measured largest longitudinal diameters of an arbitrary plurality of particles observed in a field of view of the texture of the powder under a transmission type electron microscope. Since the powder comprises superfine particles, they inevitably aggregate to one another to form superfine ceramic powder aggregates generally with a mean diameter of 1 to 30 μm, even when the powder is added in the glycol starting material by grinding the powder in a ball mill.
The polyester molded body has been made to be light weight and small in size in compliance with the improvement and development of film casting and thread spinning technologies combined with diversity of needs. However, more improvements in making the film even thinner and making the diameter of the thread even finer as well as measuring the transparency of the films and threads are urgently desired in applying the technologies. However, thin films and fine threads have not been realized in the conventional polyester molded bodies due to insufficient mechanical strength, in addition to insufficient transparency.